Firearms design involves many non-trivial challenges. In particular, firearms, such as small arms and handguns, have faced particular complications with reducing the audible and visible signature while also maintaining the desired ballistic performance.
Some accessories are designed to be mounted to the muzzle-end of a firearm barrel in one or more particular rotational orientations to accomplish a desired effect. For example, a muzzle brake redirects a portion of propellant gases sideways or rearward, with respect to the firing direction, as the gases escape from the barrel when a shot is fired. As the gases are redirected, the firearm is pushed forward in a manner that counteracts recoil of the firearm. A muzzle brake is typically mounted to a firearm barrel in a particular rotational orientation, such as to prevent gases from being redirected upward into the line of sight of the firearm operator. The manner of rotationally orienting a muzzle end accessory on the barrel is often referred to as timing the accessory to the barrel.
Suppressors are another muzzle-end mounted accessory intended to reduce the audible report of the firearm. Suppressors may include a series of baffled chambers to slow the release of pressurized gases from the barrel of the firearm and therefore reduce the audible report when discharging the firearm. The United States Bureau of Alcohol, Tobacco, Firearms, and Explosives currently defines a suppressor as any device that, when attached to the muzzle of a firearm, reduces the audible report of the firearm by a perceptible amount.